Implement HTMLMediaElement::srcObject.

Source/modules/modules.gypi

 {
   'includes': [
     '../core/core_generated.gypi',
     'modules_generated.gypi',
   ],
   'variables': {
     # Experimental hooks for embedder to provide extra IDL and source files.
     #
     # Note: this is not a supported API. If you rely on this, you will be broken
     # from time to time as the code generator changes in backward incompatible
@@ skipping 555 matching lines @@
       'mediastream/MediaConstraintsImpl.cpp',
       'mediastream/MediaConstraintsImpl.h',
       'mediastream/MediaDeviceInfo.cpp',
       'mediastream/MediaDeviceInfo.h',
       'mediastream/MediaDeviceInfoCallback.h',
       'mediastream/MediaDevicesRequest.cpp',
       'mediastream/MediaDevicesRequest.h',
       'mediastream/MediaStream.cpp',
       'mediastream/MediaStream.h',
       'mediastream/MediaStreamEvent.cpp',
-      'mediastream/MediaStreamEvent.h',
+      'mediastream/MediaStreamEvent.h',     
       'mediastream/MediaStreamRegistry.cpp',
       'mediastream/MediaStreamRegistry.h',
       'mediastream/MediaStreamTrack.cpp',
       'mediastream/MediaStreamTrack.h',
       'mediastream/MediaStreamTrackEvent.cpp',
       'mediastream/MediaStreamTrackEvent.h',
       'mediastream/MediaStreamTrackSourcesCallback.h',
       'mediastream/MediaStreamTrackSourcesRequestImpl.cpp',
       'mediastream/MediaStreamTrackSourcesRequestImpl.h',
       'mediastream/NavigatorMediaStream.cpp',
@@ skipping 446 matching lines @@
       'serviceworkers/ServiceWorkerContainerTest.cpp',
       'websockets/DOMWebSocketTest.cpp',
       'websockets/NewWebSocketChannelImplTest.cpp',
       'websockets/WebSocketDeflaterTest.cpp',
       'websockets/WebSocketExtensionDispatcherTest.cpp',
       'websockets/WebSocketExtensionParserTest.cpp',
       'websockets/WebSocketPerMessageDeflateTest.cpp',
     ],
   },
 }